The subject matter disclosed herein relates to the general field of endovascular catheters used to treat vascular pathologies and specifically to an endovascular catheter with multiple capabilities which can serve as an adjunct to surgery on vascular structures.
Stroke has plagued mankind since time immemorial. Its sudden and devastating effects were first recognized stroke as a pathologic entity by Hippocrates, often referred to as the Father of Medicine, over 2,400 years ago. Plato, Pope St. Leo, Charlemagne, Henry VIII, Woodrow Wilson, Vladimir Lenin, Sir Walter Scott, Richard Nixon and Margaret Thatcher are but a handful of historic figures who met their end as the result of stroke. Diligent postmortem studies demonstrated areas of the brain which had infarcted, presumably from interruption in circulation, although it took another seven decades to ultimately recognize that disease of the carotid arteries—which supply the majority of blood flow to the brain—was responsible for this malady in the majority of cases. Specifically, it is now known that atherosclerotic plaque along the walls of the internal carotid artery, usually just beyond the bifurcation of the common carotid artery, leads to narrowing of the lumen of the artery. This can result in stroke in two ways: first, the plaque can narrow the lumen to a dangerous point, and second, pieces of the plaque can break off, forming globules referred to as emboli.
In the first scenario, the lumen can be narrowed to a critical point, reducing the blood flow to a point that it now longer meets the metabolic demands of the brain, causing a temporary reduction in brain function. A reflex increase in the muscle tone in the arteries can restore the blood flow after a few minutes, sometimes preventing further damage. Clinically, this sequence of events can initially result in a transient but fully reversible loss of neurologic function, a phenomenon known as a “Transient Ischemic Attack,” and more commonly known as a “TIA,” or “Mini-Stroke.” It is known that this phenomenon often heralds or is a precursor to a major stroke. If such a critical reduction of blood flow continues, an extensive blood clot can form within the carotid artery, resulting in extensive permanent loss of blood flow and massive damage to the brain, clinically resulting in a stroke.
In the second scenario, the emboli break off and are then carried upstream where the arteries become smaller and smaller until a point is reached where the arteries become so small that these emboli cannot pass through. If the emboli are tiny, this may be insignificant. On the other hand, if the emboli are massive, they become lodged at a point where they stop blood flow to a major portion of the cerebral circulation, resulting in the loss of blood flow to large areas of the brain. It became apparent that if treatment could be instituted at a point when the patient first becomes symptomatic with TIA's perhaps the permanent damage from a stroke could be avoided.
On that basis, in 1953 the great cardiovascular surgeon Michael De Bakey performed the first carotid endarterectomy (CEA). This is a surgical procedure in which the surgeon temporarily clamps off the common, internal and external carotid arteries and then incises the affected artery and removes the offending plaque prior to sewing the artery closed. By the 1980's, this had become one of the cornerstones in the treatment of stroke. However, a “double-edged sword” is that although CEA is performed to prevent future strokes in a patient, stroke is also the main complication CEA. Specifically, the rate of stroke as a complication of this surgery ranges from 2-7%. This is thought to be related to either the temporary loss of blood flow to the cerebral hemisphere, or emboli arising from manipulation of the artery.
In an attempt to reduce the perioperative stroke rate, the 1970's witnessed the introduction of intraoperatively placing a tube or “intravascular shunt,” which carries blood from the common carotid artery at a point prior to where the artery is clamped off to the internal carotid artery at a point beyond where this artery is clamped off, and thus maintain flow to the brain. However, the use of intraoperative/intravascular shunting remains controversial. While the theoretical basis for the use of shunting is recognized by all, detractors of this technique point out that large, controlled studies have never proven, incontrovertibly, that shunting reduces the perioperative stroke rate. Moreover, a number of technical difficulties associated with the use of shunts have been cited by multiple authors. These shortcomings include the technical difficulties in positioning the shunt, the variability of time required for the placement, the inconstancy of the blood flow during surgery, and the need to clamp off the carotid to introduce and remove the shunt. With a persisting stroke rate being reported even with the use of intravascular shunts, the question of whether CEA was truly better than medical therapy alone needed to be addressed.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.